Pumps, commonly known as jet or centrifugal pumps, which provide water from a well to a home are, of course, known in the art. Such pumps include a pump casing having a suction inlet and discharge outlet, an impeller in the casing driven by a motor, and a diffuser, venturi and nozzle also in the casing. Typically, the venturi directly receives water supplied from the well through the suction inlet of the casing, and water at high pressure is recirculated from the impeller through the nozzle. The combined action of high velocity rotation of the impeller and high pressure recirculation of a fraction of its water output via the casing through the nozzle to the venturi produces a vacuum condition at the suction inlet of the casing. This allows atmospheric pressure to push water through the suction pipe from the bottom of the well to the casing suction inlet and feed water therefrom through the venturi tube to the impeller inlet and out through the discharge outlet.
These types of pumps, while operating satisfactorily to achieve the level of performance for which they were designed, are not without their problems. For example, such pumps usually require a large complicated casing which is difficult to cast and machine. Moreover, the assembly of the parts located in the casing is often difficult to accomplish, particularly to assure the proper location of certain components which is critical to the operation of the pump. For example, the distance between the nozzle and the venturi is critical and in some prior art designs, it was difficult to assure that every pump was assembled with the proper venturi/nozzle relationship.
Such is particularly true in those designs where low pressure water first enters the nozzle and passes through the venturi to the impeller from which the water is recirculated in the casing to the throat of the venturi in the small space between the venturi and the nozzle. In this instance the venturi is usually threaded onto the impeller and the spacing between the nozzle and the other end of the venturi is critical. However, in these situations manufacturing tolerances dictate that the distance between the other end of the venturi and the nozzle cannot always be the same thereby changing the performance of each pump being assembled. In addition, in such situations perfect threaded engagement and a perfectly round impeller hub was required. Otherwise, the venturi would wobble thereby providing inconsistent flow rates as the relationship between the venturi and the nozzle would constantly vary upon each rotation of the impeller.
In short, despite the popularity of the prior art designs, the need exists for a pump which is easy to manufacture and assemble and at the same time assure a constant relationship between the nozzle and the venturi so that every pump assembled will provide a constant flow rate and otherwise meet specifications.